feat(java): integrate lance-namespace to lancedb Java SDK (#2524)

java/lance-namespace/pom.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>com.lancedb</groupId>
+        <artifactId>lancedb-parent</artifactId>
+        <version>0.21.2-beta.0</version>
+        <relativePath>../pom.xml</relativePath>
+    </parent>
+
+    <artifactId>lancedb-lance-namespace</artifactId>
+    <name>${project.artifactId}</name>
+    <description>LanceDB Java Integration with Lance Namespace</description>
+    <packaging>jar</packaging>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.lancedb</groupId>
+            <artifactId>lance-namespace-core</artifactId>
+        </dependency>
+    </dependencies>
+</project>

java/lance-namespace/src/main/java/com/lancedb/lancedb/LanceDbRestNamespaces.java

@@ -0,0 +1,146 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.lancedb.lancedb;
+
+import com.lancedb.lance.namespace.LanceRestNamespace;
+import com.lancedb.lance.namespace.client.apache.ApiClient;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+/** Util class to help construct a {@link LanceRestNamespace} for LanceDB. */
+public class LanceDbRestNamespaces {
+  private static final String DEFAULT_REGION = "us-east-1";
+  private static final String CLOUD_URL_PATTERN = "https://%s.%s.api.lancedb.com";
+
+  private String apiKey;
+  private String database;
+  private Optional<String> hostOverride = Optional.empty();
+  private Optional<String> region = Optional.empty();
+  private Map<String, String> additionalConfig = new HashMap<>();
+
+  private LanceDbRestNamespaces() {}
+
+  /**
+   * Create a new builder instance.
+   *
+   * @return A new LanceRestNamespaceBuilder
+   */
+  public static LanceDbRestNamespaces builder() {
+    return new LanceDbRestNamespaces();
+  }
+
+  /**
+   * Set the API key (required).
+   *
+   * @param apiKey The LanceDB API key
+   * @return This builder
+   */
+  public LanceDbRestNamespaces apiKey(String apiKey) {
+    if (apiKey == null || apiKey.trim().isEmpty()) {
+      throw new IllegalArgumentException("API key cannot be null or empty");
+    }
+    this.apiKey = apiKey;
+    return this;
+  }
+
+  /**
+   * Set the database name (required).
+   *
+   * @param database The database name
+   * @return This builder
+   */
+  public LanceDbRestNamespaces database(String database) {
+    if (database == null || database.trim().isEmpty()) {
+      throw new IllegalArgumentException("Database cannot be null or empty");
+    }
+    this.database = database;
+    return this;
+  }
+
+  /**
+   * Set a custom host override (optional). When set, this overrides the default LanceDB Cloud URL
+   * construction. Use this for LanceDB Enterprise deployments.
+   *
+   * @param hostOverride The complete base URL (e.g., "http://your-vpc-endpoint:80")
+   * @return This builder
+   */
+  public LanceDbRestNamespaces hostOverride(String hostOverride) {
+    this.hostOverride = Optional.ofNullable(hostOverride);
+    return this;
+  }
+
+  /**
+   * Set the region for LanceDB Cloud (optional). Defaults to "us-east-1" if not specified. This is
+   * ignored when hostOverride is set.
+   *
+   * @param region The AWS region (e.g., "us-east-1", "eu-west-1")
+   * @return This builder
+   */
+  public LanceDbRestNamespaces region(String region) {
+    this.region = Optional.ofNullable(region);
+    return this;
+  }
+
+  /**
+   * Add additional configuration parameters.
+   *
+   * @param key The configuration key
+   * @param value The configuration value
+   * @return This builder
+   */
+  public LanceDbRestNamespaces config(String key, String value) {
+    this.additionalConfig.put(key, value);
+    return this;
+  }
+
+  /**
+   * Build the LanceRestNamespace instance.
+   *
+   * @return A configured LanceRestNamespace
+   * @throws IllegalStateException if required parameters are missing
+   */
+  public LanceRestNamespace build() {
+    // Validate required fields
+    if (apiKey == null) {
+      throw new IllegalStateException("API key is required");
+    }
+    if (database == null) {
+      throw new IllegalStateException("Database is required");
+    }
+
+    // Build configuration map
+    Map<String, String> config = new HashMap<>(additionalConfig);
+    config.put("headers.x-lancedb-database", database);
+    config.put("headers.x-api-key", apiKey);
+
+    // Determine base URL
+    String baseUrl;
+    if (hostOverride.isPresent()) {
+      baseUrl = hostOverride.get();
+      config.put("host_override", hostOverride.get());
+    } else {
+      String effectiveRegion = region.orElse(DEFAULT_REGION);
+      baseUrl = String.format(CLOUD_URL_PATTERN, database, effectiveRegion);
+      config.put("region", effectiveRegion);
+    }
+
+    // Create and configure ApiClient
+    ApiClient apiClient = new ApiClient();
+    apiClient.setBasePath(baseUrl);
+
+    return new LanceRestNamespace(apiClient, config);
+  }
+}